研究 IL-1β 對初代培養大鼠胚胎皮質神經細胞之電生理的影響

Abstract

介白素-1β (IL-1β) 是一種促發炎的細胞激素，普遍認為在神經發炎相關的神經退化性疾病中，扮演重要的調控角色；目前也有研究發現，IL-1β 參與在神經損傷所引起的癲癇和興奮性毒性導致的神經細胞死亡的機制當中，因此 IL-1β 也可能具有調節神經傳導的作用。絕大多數的研究著重在神經細胞與神經膠細胞分泌的 IL-1β，在長時間的作用下對神經細胞存活率的影響，然而對神經電生理活性的影響則不清楚。因此在本研究中，利用膜片鉗技術，探討 IL-1β 對初代培養大鼠胚胎皮質神經細胞電生理活性的影響。加入 IL-1β (1 & 10 ng/ml) 後，自發興奮性突觸後電流的頻率增加，但電流峰值下降。而改變膜電位探討流入胞內的鈉離子流結果發現，IL-1β (1 ng/ml) 增加了電流峰值，在 -20 mV，由 -46.5 pA/pF ± 34.9 顯著性增加至 -54.1 pA/pF ± 30.4。在鈉離子通道活化曲線中，IL-1β會導致V1/2向左偏移，從 -40.5 mV ± 15.1 到 -44.6 mV ± 15.2 (n = 5, p < 0.05, IL-1β 1 ng/ml)；在穩態鈉離子通道去活化曲線中，IL-1β同樣使V1/2向左偏移，從 -34.9 mV ± 5.7 到-40.2 mV (n = 6, p < 0.05, IL-1β 1 ng/ml)。總結來說，IL-1β會藉由提升鈉離子通道對膜電位的敏感度，增強神經細胞的電生理活性，顯示IL-1β不只參與神經發炎的調控，也透過對神經傳遞的調節，影響神經電生理。

Interleukin-1β (IL-1β) is a pro-inflammatory factor, which belongs to IL-1 family and acts as a key role in the neuroinflammatory responses. The release of IL-1β has been reported in neuronal injuries with the accompaniment of epileptogenesis and excitotoxic neuronal death suggesting the possible role IL-1β plays in regulating the neurotransmission. Most studies emphasize the long-term effects of IL-1β released from glia and neurons on the viability of neurons, however, the immediate effects of IL-1β on the electrical properties of neurons remain unclear. In this study, we characterized the effects of IL-1β in the electric activities of primary cultured rat embryonic cortical neurons by patch-clamp technique under whole-cell mode. The application of IL-1β (1 and 10 ng/ml) slightly increased the frequency of the excitatory post-synaptic currents in 3 min. By step-depolarizing the membrane potential from a holding potential of -100 mV, IL-1β marginally enhanced the peak inward current contributed by Na+ at -10 mV. The activation curve of this inward Na+ current showed a significant leftward shift in V1/2 from -40.5 ± 15.1 to -44.6 ± 15.2 mV (n = 5, p < 0.05, IL-1β 1 ng/ml). Similarly, IL-1β shifted the steady-state Na+ channel inactivation curves from -34.9 ± 5.7 to -40.2 ± 7.1 in the V1/2 (n = 6, p < 0.05, IL-1β 1 ng/ml). IL-1β showed no effect on the recovery time constant of the Na+ channel from inactivation to closed state. In summary, IL-1β can enhance the electrical responses of cultured neurons by increasing the sensitivities of Na+ channels to the membrane potential. Therefore, while IL-1β regulates the downstream neuroinflammatory responses, it also augments the neuronal electrical activity and neurotransmission.